Medical Radiology and Radiation Safety. 2021. Vol. 66. № 6. P. 119-120

A.P. Ermilov

THE PHENOMENON OF FUEL PARTICLES IN CONSEQUENCES OF THE CHNPP ACCIDENT
(OVERVIEW)¹

LLC "STC Amplitude"

Contact person: Alexey Pavlovich Ermilov, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

The subject of the study was the consequences of the explosion of the core of the RBMK power uranium-graphite reactor at the Chernobyl NPP - a unique event and, we hope, unrepeatable.

As a result of a nuclear explosion that destroyed the fourth unit of the Chernobyl nuclear power plant, immediately after the explosion, a cloud appeared in the air above the station’s territory, containing an aerodispersed system that included aerosols formed during the explosion. The explosion occurred before the proposed reloading of the reactor core. Thus, the emission cloud contained radioactive fission and uranium activation products that had accumulated in the fuel of the reactor core during the campaign. The east wind on the night of 04/26/1986 carried the explosion cloud to the west, leaving a radioactive trail from aerosol fallouts on the earth’s surface.

The immediate cause of the accident was the use of an emergency protection system that night to shut down the reactor. The reactor exploded when the emergency protection rods were inserted into the core2. The design of the emergency protection rods was such2 that it was their introduction into the core under the prevailing conditions that initiated the development of an uncontrolled fission chain reaction in the reactor core. The explosion ended with the termination of neutron thermalization due to the destruction of the graphite stack.

In contrast to the explosion of a nuclear charge occurring on prompt fission neutrons with an average energy of ~ 2 × 106 eV, an uncontrolled chain fission reaction in the reactor core developed on thermalized prompt neutrons with an energy of ~ 2.5 × 10-2 eV, i.e. with a chain transfer rate at least ~ 104 times slower. “Competition” between the development of a nuclear explosion on the one hand and the destruction of the graphite stack by an explosion, on the other, led to a nuclear explosion in the reactor core with TNT equivalent, according to various estimates, on the order of ~ 10-30 t TNT.

Within 36 hours, 106 people with indications of acute radiation sickness, who were at the time of the explosion on the territory and in the premises of the Chernobyl nuclear power plant, were hospitalized in Clinical Hospital No. 6 of the 3rd GU of the USSR Ministry of Health in Moscow. Of these, 26 patients died within three months after the accident. For all patients in the clinic, the values ​​of the external radiation dose were assessed according to the hematological parameters. As for internal exposure, due to the lack of necessary information about the nature of the incident, its dose contribution to the fate of the victims had to be assessed by clinical indicators. The results of clinical observations during the stay of the victims in the hospital are summarized in a monograph published in 2011: A.K. Guskova, I.A. Galstyan, I.A. Gusev «The accident of the Chernobyl nuclear power plant (1986-2011): consequences for health, a doctor’s thoughts.» Quote: “Dosimetric studies of the content of cesium and iodine in the body were carried out both directly in the wards and during the expansion of the regime in the laboratory on the radiation meters of the human body ... These qualified measurements confirmed the extreme rarity of significant incorporation of radionuclides and the predominant importance of external radiation in the development of changes in the state of health victims «.

The above conclusion about the insignificance of internal exposure does not seem to be indisputable. Due to the destruction caused by the explosion, immediately after the explosion, a «draft» arose that pulled the aero-dispersed mixture of dispersed nuclear fuel from the destroyed reactor through the working rooms, where the night shift of Chernobyl NPP workers was located, to a ventilation pipe 110 m high. This was evidenced by the considerable efforts spent on deactivation of the ventilation system of the working rooms of the Chernobyl nuclear power plant when the third power unit was launched almost a year after the explosion of the fourth power unit. From general considerations, it seems obvious that the aerodispersed mixture also contained a fraction of coarsely dispersed insoluble aerosols of nuclear fuel dispersed by the explosion. During inhalation, the upper respiratory tract is exposed to the predominant deposition of coarse aerosols. The main mechanism of their natural purification is mucociliary transport of deposited aerosols in the gastrointestinal tract for several tens of minutes to a day after admission, with a further delay of ~ 2 days in the gastrointestinal tract and fecal excretion (transient excretion). It is obvious that the «qualified measurements at the SIR», carried out several days later, were late, and this significant factor of internal irradiation remained underestimated. The same can be said about the results of postmortem measurements of activity in the tissues and organs of the deceased.

Based on the analysis of the results of our own studies of accidental fallouts and the results of clinical observations carried out in Clinical Hospital No. 6, the presence of a significant dose contribution from the transit of fuel particles was established, and its assessment was made for those who were at the time of the accident in the premises of the Chernobyl NPP and later died. It was shown that the cause of death of some of them was the intestinal form of acute radiation sickness, caused by the combined effect of external photon radiation and beta radiation of inhaled radionuclides on the reproduction system of the single-layer columnar epithelium of the small intestine during transit of inhaled fuel particles through the gastrointestinal tract.

An explanation was obtained for the cause of the «Chernobyl cough» - a deterministic effect that spread in the summer of 1986 and in the summer of 1987 among people who found themselves in the territories subjected to intensive emergency radioactive fallout from the Chernobyl nuclear power plant.

Thus, it was possible to add essential details to the general picture of one of the most significant radiation incidents of the atomic age.

Key words: Chernobyl nuclear power plant, accident, nuclear fuel, fuel particles, "hot" particles, "volatile" fraction, acute radiation sickness

For citation: Ermilov AP. The Phenomenon of Fuel Particles in Consequences of the CHNPP Accident. Medical Radiology and Radiation Safety. 2021;66(6):119-120. https://medradiol.fmbafmbc.ru/journal_medradiol/abstracts/2021/6/ap_ermilov.pdf

DOI: 10.12737/1024-6177-2021-66-6-119-120

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The full version of the article by Ermilova A.P. published in the public domain on the journal's website
https://medradiol.fmbafmbc.ru/journal_medradiol/abstracts/2021/6/ap_ermilov.pdf